In the plumbing industry, multi-purpose composite pressure tubing and the applications for such tubing have been developing rapidly. Composite tubing is a multi-layer tubing which generally consists of an inner layer of plastics material, an intermediate layer of aluminium alloy and an outer layer of a plastics material. Composite tubing provides the advantages of both metal and plastic and is useful in a wide range of applications because of its flexibility and strength, especially its resistance to rupture when subjected to relatively high temperature and pressures. Multi-purpose composite pressure tubing can be used in both indoors and outdoors, cast in concrete, concealed in walls, floors and ceilings or surface mounted. It can be used for hot and cold water distribution, under surface floor heating, ice melt systems for sidewalks and driveways, air-conditioning systems, compressed air and industrial process piping. Composite tubing is available, for example, from IPEX, which produces a tubing (KITEC .RTM.) consisting of an aluminium tubing laminated between two layers of polyethylene. To produce this tubing, an aluminium strip is formed, overlapped and then ultrasonically welded. Layers of polyethylene are then applied with an adhesive to form a bond with the aluminium tubing. The result is a tubing that does not rust, corrode or tuberculate. Fittings are commercially available for use with this composite tubing and an example of those fittings is described below.
In the general prior art, the use of O-rings to provide a seal between an exterior of a pipe and an interior of a connecting pipe is known. Canadian Patent No. 993,010 entitled METER RISER ASSEMBLY, which issued on Jul. 13, 1976 to Mueller Co., for example, discloses a meter riser assembly for use in connecting a fluid meter with a plastic service line. One embodiment shown in FIG. 6 discloses two O-rings adapted to provide a seal between an exterior of a coated metal pipe and an interior of the service line.
U.S. Pat. No. 3,112,939, entitled THREADLESS TUBING CONNECTOR, which issued to Graham on Dec. 3, 1963; U.S. Pat. No. 4,603,890 entitled BARBED TUBING CONNECTOR, issued to Huppee on Aug. 5, 1986; U.S. Pat. No. 5,480,196 entitled DUCTILE IRON PIPE JOINT EMPLOYING A COUPLING AND COUPLING THEREFOR which issued to Adams, Jr. on Jan. 2, 1996 discloses various applications of O-ring seals associated with tubing connectors. Huppee also discloses in his patent a tensioning strip adjustably surrounding the tubing in registry with the O-rings to exert radial pressure on the tubing to compress the O-rings. The tension strip is normally used in association with a tubing that has a high degree of elasticity.
Although each of these prior art patents relate to O-ring seals associated with threadless tubing connectors, they are not adapted to be used with composite tubing to provide fast installation and a dependable fluid tight seal. Therefore, it is desirable to provide a tubing connector which can be easily and quickly installed in a composite tubing and provides a dependable fluid tight seal even in a high pressure and high temperature application such as an in-floor heating system.